1. Field of the Invention
The present invention is related to a machine press in which a ram is movable up and down over a work-piece supporting portion. The work-piece supporting portion is formed on one side of a frame on which the ram is movably supported. The ram is driven under the swinging motion of a lever provided on the frame.
2. Description of the Prior Art
Conventional machine presses include those disclosed in published and examined Utility Model Application No. Sho. 42(1967)-11916 and published unexamined Utility Model Patent Application No. Sho. 54(1979)-81574. These machine presses comprise a partitioned frame having a vertically extending box shape, a crank shaft supported in the lower part of said frame, and a crank pin which turns along one side of the partition connected to a slider supporting member provided on the bottom of a lever which is separately supported, the lever being swung along one side of the partition.
The machines also include a large gear which rotates on the other side of the partition and is connected to the other end of said crank shaft. The large gear is connected to a driving gear which rotates at the upper part of the partition. A rotary shaft projects from the frame at both ends thereof, has the driving gear fitted thereto and is supported in the upper part of the frame. A clutch is operatively connected to one end of said rotary shaft with a driving wheel of the clutch driven by a motor while a brake is operatively connected to the other end of the shaft.
The conventional machine presses described above are deficient in that their structure is complicated. More particularly, because the crank shaft is driven by a gear train consisting of a large gear, a mid gear and a driving gear, and because a rotary shaft which is provided with a clutch and a brake and which drives the gear train extends horizontally in the upper part of the frame, it is impossible to increase the strength of the lever because the swinging stroke of the lever which moves the ram up an down is limited and accordingly,the lever is limited to having small width.
Moreover, due to the aforementioned structure, the center of gravity of the machine is high and the lever which moves the ram up and down swings in a state biased toward one side of the frame, causing dynamic unbalance in the right and left directions.